Deanne,
The Schoolshape Language Lab might help you. It gives you an online
'canvas' on which to place
1. your stimulus, such as picture, text, video etc.
2. your required student response, such as audio, audio gap-fill, video,
text etc.
It allows you to arrange tiered or differentiated tasks for groups or
individuals and you can set the date and time for commencement and
completion of the task, and also the length of permissible recording.
It also works on iPads.
There is a free version.
Instructions at
http://schoolshape.com/how-to-guideRegards,
Peter